Optimizer interface and sample implementation (#19)

Reviewed-on: Rubydragon/MetagraphOptimization.jl#19
Co-authored-by: Anton Reinhard <anton.reinhard@proton.me>
Co-committed-by: Anton Reinhard <anton.reinhard@proton.me>

src/operation/clean.jl

@@ -13,18 +13,18 @@ function find_fusions!(graph::DAG, node::DataTaskNode)
         return nothing
     end
 
-    if length(node.parents) != 1 || length(node.children) != 1
+    if length(parents(node)) != 1 || length(children(node)) != 1
         return nothing
     end
 
-    child_node = first(node.children)
-    parent_node = first(node.parents)
+    child_node = first(children(node))
+    parent_node = first(parents(node))
 
     if !(child_node in graph) || !(parent_node in graph)
         error("Parents/Children that are not in the graph!!!")
     end
 
-    if length(child_node.parents) != 1
+    if length(parents(child_node)) != 1
         return nothing
     end
 
@@ -44,11 +44,11 @@ Find node fusions involving the given compute node. The function pushes the foun
 """
 function find_fusions!(graph::DAG, node::ComputeTaskNode)
     # just find fusions in neighbouring DataTaskNodes
-    for child in node.children
+    for child in children(node)
         find_fusions!(graph, child)
     end
 
-    for parent in node.parents
+    for parent in parents(node)
         find_fusions!(graph, parent)
     end
 
@@ -123,7 +123,10 @@ end
 
 Sort this node's parent and child sets, then find fusions, reductions and splits involving it. Needs to be called after the node was changed in some way.
 """
-function clean_node!(graph::DAG, node::Node)
+function clean_node!(
+    graph::DAG,
+    node::Union{DataTaskNode{TaskType}, ComputeTaskNode{TaskType}},
+) where {TaskType <: AbstractTask}
     sort_node!(node)
 
     find_fusions!(graph, node)